1. Field of the Invention
The present invention relates to a system and a method for a uniform deflecting hub.
2. Background Art
Referring to FIG. 1, a diagram illustrating an exploded, perspective view of a conventional magnetic media (e.g., tape) reel (or spool) 10 is shown from an upper vantage point. The reel 10 includes a hub/flange 12 having a hub 14 integral with a lower flange 16, and an upper flange 18 that is joined (e.g., attached, bonded, etc.) to the hub 14. The hub 14 has a lip 20a at an interface to the lower flange 16, and a lip 20b at the attachment to the upper flange 18. The hub 14 has a spooling cylinder 22 between the lips 20a and 20b and magnetic media (not shown) is wound on the reel 10 between inner surfaces of the flanges 16 and 18.
Referring to FIG. 2, a diagram illustrating a perspective view of the conventional reel 10 as assembled is shown from a lower vantage point. The reel 10 is generally formed from a plastic. The upper flange 18, is generally attached to the hub 14 by ultrasonic welding, however, any appropriate bonding such as spin welding, hot plate welding, induction welding, adhesion, etc. may be implemented. The hub 14 has a hat-shaped inner coupling 30 that interfaces with a media drive (not shown) when the reel 10 is mounted to (or in) the media drive. The inner coupling 30 has a hole 32 at the center that engages a shaft (or spindle) in the media drive.
Referring to FIG. 3, a diagram illustrating a sectional view of the hub/lower flange 12, taken at lines 50—50 of FIG. 1, is shown. The hub/flange 12 has a thickness, T. The inner coupling 30 has an outer surface that is essentially flush with an outer surface of the lower flange 16 near the hole 32, and the inner coupling 30 is offset upward (i.e., towards the upper lip 20b) by an offset amount, t, where the inner coupling 30 is integrated with the spooling cylinder 22.
The hub 14 of the media reel 10 is subjected to pressure from the magnetic media as the media is wound onto the spooling cylinder 22. The pressure from the magnetic media increases as the number of wraps of magnetic media increases. The pressure on the hub 14 is a function of hub stiffness. Therefore, a slightly compliant hub is desirable to reduce the pressure on the magnetic media.
The conventional cartridge hub 14, as shown in FIGS. 1–3, varies greatly in stiffness from top to bottom of the winding surface of the cylinder 22 (i.e., between lip 20a and lip 20b). The integral lower flange 16 and inner coupling 30 both add radial stiffness to the bottom of the hub 14. The upper flange 18 (which is joined to the hub/flange 12) does not significantly stiffen the top (i.e., the lip 20b region) of the hub 14. Therefore, under winding pressure (as described below in connection with FIG. 6a), the radial deflection at the top of the hub 14 (i.e., the lip 20b region) is greater than the bottom (i.e., the lip 20a region) resulting in a taper (i.e., the hub 14 has a smaller diameter at the top than at the bottom). The taper of the hub 14 can cause a tension gradient across the width of magnetic media. The taper can adversely affect head-to-media spacing and read-write error margins during media drive operations.
Future media drives are expected to use longer, thinner media (i.e., magnetic media) resulting in greater pressure on the media reel hub. Thus, there exists a need and an opportunity for a system and a method to improve hub performance for media reels. Specifically, a media reel having a uniform deflecting hub would be desirable for use with magnetic media.